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DEVICE AND METHOD FOR REDUCING THE DAZZLE EFFECT IN A ROOM OF A BUILDING

Abstract

A device comprising a dimmable panel comprising a plurality of
individually dimmable cells attached to a window glass, an optical sensor
to detect an image of one or more objects, a computation unit,
communicably coupled to the dimmable panel and the optical sensor, to: i)
cause to darken one or more cells of the plurality of individual dimmable
cells of the dimmable panel, ii) cause the optical sensor to capture an
image of the one or more objects, and, iii) determine, based on the
image, whether a shadow is cast on the one or more objects due to the one
or more darkened cells.

16. A device, comprising: a dimmable panel comprising a plurality of
individually dimmable cells attached to a window glass; an optical sensor
to detect an image of one or more objects; and a computation unit,
communicably coupled to the dimmable panel and the optical sensor, to: i)
cause to darken one or more cells of the plurality of individual dimmable
cells of the dimmable panel, ii) cause the optical sensor to capture an
image of the one or more objects, and iii) determine, based on the image,
whether a shadow is cast on the one or more objects due to the one or
more darkened cells.

17. The device according to claim 16, wherein the computation unit is
further to identify one or more shadow cells of the plurality of
individually dimmable cells of the dimmable panel which cause that the
shadow is cast on the one or more objects by darkening the one or more
shadow cells, when illuminated by a light source.

18. The device according to claim 16, wherein the computation unit is
further to repeat the steps i) to iii) for different cells of the panel
until the shadow is cast on the one or more objects.

19. The device according to claim 16, wherein the one or more objects are
one or more persons in a room of a building, and wherein the room is
illuminated by a light source through the winder glass.

20. A device, comprising: a dimmable panel comprising a plurality of
individually dimmable cells attached to a window glass; a first optical
sensor which to detect a first image of one or more objects; a second
optical sensor to detect a second image of at least one light source; and
a computation unit, communicably coupled to the dimmable panel, the first
optical sensor and the second optical sensor, to: cause the first optical
sensor to capture the first image of the one or more objects, identify,
based on the first image, a respective position of the one or more
objects, cause the second optical sensor to capture the second image of
the at least one light source, identify, based on the second image, a
position of the at least one light source, and cause to darken, based on
the position of the one or more objects and the position of the at least
one light source, one or more cells of the plurality of individual
dimmable cells.

21. The device according to claim 20, wherein the one or more objects are
one or more persons in a room of a building, and wherein the room is
illuminated by a light source through the winder glass.

22. A method comprising: causing, by a processor, to darken an area of a
dimmable panel, wherein the dimmable panel is arranged between one or
more objects and a light source; detecting an image of the one or more
objects; and determining, based on the image, whether a shadow is cast on
the one or more objects due to the one or more darkened cells.

23. The method according to claim 22, wherein the one or more objects are
one or more persons in a room of a building, and wherein the room is
illuminated by the light source through a winder glass to which the area
of the dimmable panel is attached.

24. A method comprising: detecting, by a processor, a first image of the
one or more objects; identifying, based on the first image, a respective
position of the one or more objects; detecting a second image of at least
one light source; identifying, based on the second image, a position of
the at least one light source; and causing to darken, based on the
position of the one or more objects and the position of the at least one
light source, an area of a dimmable panel arranged between the at least
one light source and the one or more objects.

25. The method according to claim 24, wherein the one or more objects are
one or more persons in a room of a building, and wherein the room is
illuminated by the light source through a winder glass to which the area
of the dimmable panel is attached.

26. The method according to claim 24, wherein the dimmable panel
comprises a cell matrix having a plurality of separately dimmable cells;
and wherein the darkening of the area of the dimmable panel comprises
darkening of one or more cells of said plurality of cells.

27. The method according to claim 24, wherein the at least one light
source is a light source outside of the building, and wherein the light
source is one of a sun or a reflection of the sun.

28. The method according to claim 25, wherein the darkening of the area
is carried out such that a light of the at least one light source casts
the shadow on heads of the one or more persons.

29. The method according to claim 24, wherein the dimmable panel
comprises a liquid crystal display (LCD) film which is one of applied to
the window glass or incorporated between two layers within the window
glass.

30. The method according to claim 26, further comprising in a search
phase, determining one or more shadow cells of the plurality of
separately dimmable cells, the darkening of which casts the shadow from
the light source to the one or more objects in the room, wherein the
determining comprises iterating the steps of darkening, detecting and
determining for different cells of the panel.

31. The method according to claim 30, wherein in one iteration, a subarea
of a plurality of separately dimmable cells of the panel is darkened; the
subarea is excluded from determining of the one or more shadow cells
responsive to determining that no shadow is cast on the one or more
objects in a room; and the determination of the one or more shadow cells
is limited to the subarea responsive to determining that a shadow is cast
on the one or more persons in the room.

32. The method according to any one of claim 31, further comprising in a
darkening phase, darkening the one or more shadow cells to reduce a glare
effect from the light source to the one or more objects in the room; and
cyclically repeating the search phase and the darkening phase.

33. The method according to claim 32, wherein the one or more shadow
cells for the current cycle are predicted from the one or more shadow
cells of the one or more preceding cycles.

34. The method according to claim 33, further comprising: determining an
overall image, which includes all persons in the room including their
surroundings, wherein the overall image is determined with the panel shut
off; determining an area of one or more persons in the room; determining
an overall brightness level from the brightness of the overall image;
determining a facial brightness level from the brightness level of the
overall image in the area of the one or more persons; and detecting a
glare effect on the one or more persons in the room by the light source
based on the facial brightness level and overall brightness.

[0002] This document relates to devices and methods for avoiding, lowering
or reducing the glare effect in rooms by external light sources, in
particular the sun and reflections of the sun, and the heat regulation of
rooms.

BACKGROUND

[0003] The number of persons with an office workplace is steadily
increasing. A large part of the workplace is exposed to the sun, which,
besides desirable factors, may lead to undesirable glare effects.
Distracting solar radiation can lead to a constant control of the shades
and thus a frequent interruption of the working flow.

[0004] In general, glare situations can be annoying for persons in a room
and can lead to a cutback in performance. For example, glare effect by a
light source, such as the sun, can be annoying for a person reading,
watching TV, working--especially when working on a desk and/or working on
a computer-, eating, having a conversation with other persons or doing
other activities.

[0005] In order to prevent light from falling through a transparent window
on persons, in particular in the face, on the head or on the upper body
of persons, which are in a room of a building, there are now some devices
such as, for example, sun screens, sun blinds, blinds, dark adhesive
films for transparent windows, electrically controlled shadeable windows
and tinted windows.

[0006] Earlier devices have specific disadvantages, such as an
unchangeable constant light damping, a complete darkening of the entire
viewing area of a transparent window pane by coloring or tinting, or a
complete optical suppression by the dimming means.

[0007] Darkening devices, such as blinds, cause the entire room to be
darkened and not just the part that is relevant to the darkening. The
contact to the outside is lost due to this darkening.

[0008] Often automatic blinds are raised in strong winds to prevent
damage. For this reason, additional internal Venetian blinds are often
used. The room heats up unnecessarily since the sun rays are blocked only
after passing the window. In addition, the contact to the outside is
lost.

[0009] Other darkening devices, such as electrochromic glazing, each
darken an entire room, even when this is a disadvantage, for example
during winter when warming by the sun is desired. Furthermore,
electrochromic glazing has a considerable disadvantage with respect to
the switching speeds; they switch very slowly. Furthermore, windows can
only be darkened over a large area. For now, individual segments are not
switchable, since switching signals with this technology would interfere
with neighboring cells. A switching cycle takes up to 15 min. A selective
fast darkening is thus not feasible.

[0010] Furthermore, darkening of the entire room (e.g. by blinds) can lead
to a room-internal source of light, in particular for electric light,
such as, for example, a light bulb, a fluorescent lamp, an uplight, a
light-emitting diode lamp or an LED lamp or any other source of light,
being switched on for better vision for the persons in the room, which
would be avoidable with better use of the light from outside the
building. Operating the indoor light source may require electrical power,
which may involve costs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure is illustrated by way of examples, and not
by way of limitation, and may be more fully understood with references to
the following detailed description when considered in connection with the
figures, in which:

[0012] FIG. 1 shows a system for avoiding a glare effect according to an
embodiment of the present disclosure;

[0013] FIG. 2 shows a system for avoiding a glare effect according to an
embodiment of the present disclosure;

[0014] FIG. 3 shows a dimmable panel according to an embodiment of the
present disclosure;

[0015] FIG. 4 describes an exemplary method for avoiding/reducing a glare
effect according to an embodiment of the present disclosure; and

[0016] FIG. 5 describes a further exemplary method for avoiding/reducing a
glare effect according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0017] The present document addresses the above disadvantages and
describes systems and methods for avoiding the glare effect by strong
external light sources while simultaneously using the external light
sources to increase the general brightness in the room.

[0018] In addition, the room temperature in buildings can be well
regulated by the present disclosure. In today's endeavors to avoid energy
consumption, this system allows for simple heat regulation by suitable
shading. In contrast to the slow switching techniques so far, it can be
responded very quickly to changes of the solar radiation and the room
temperature can be controlled ideally. This results in a considerable
savings potential for room climate control.

[0019] The described systems and methods of the present disclosure can
lead to increased comfort in the workplace and thus to an improved
performance of the employees in a company. The described systems and
methods use image analysis to calculate the position of persons in the
room and thus to determine a suitable shadow position, and the control of
a selectively dimmable panel which is attached to a window pane of a
room.

[0020] The described systems are capable of variably darkening respective
areas of a window pane of buildings dependent on external light sources
at any desired distances and positions so that only a reduced portion of
the incident light reaches the persons in a room. Special application
situations are sunny days with direct insolation into a room. A further
application situation for the described devices is glare effects caused
by reflections of the sun from other buildings, which leads to glare
effect of the persons in a room. In such cases of glare, the described
systems search, based on an electronic-optical feedback structure, the
area(s) on the window pane between the detected persons in a room and the
external light sources to be darkened, so that the area(s) can be
selectively darkened to avoid or reduce a glare effect situation. The
degree of darkening typically ensures that the glaring source of light
(e.g. the sun) is dampened to such an extent that pleasant working is
possible also at a screen workplace, while the remaining area of the
window pane or the window panes remains completely transparent for view.
The result of the selective darkening is not only the protection of the
persons at the workplace from glare effect, but also a natural increase
of the working ergonomics (by avoiding the complete darkening of the
entire room). This means that the persons in a room have the opportunity
not to lose contact with the outside, which increases quality of life.

[0021] According to one aspect of this document, a device for reducing the
glare effect of a light source for persons in a room of a building is
described.

[0022] The room can be, for example, an office space, a meeting room, a
secondary room, a hallway, a school room, a lecture hall, a study room, a
living room or any other room. The light source is, for example, the sun
or reflected sunlight from other buildings. It should be noted that the
device may be adapted to darken a plurality of glaring light sources
(e.g. a plurality of reflections) and the darkening may be performed for
a plurality of persons in a room.

[0023] The building can be an office building, a school building, a
university building, a library, a museum building, a department store, a
private house (such as a single-family house, a multi-family house, a
terraced house, a town house, a tenement house or any other private
house), a tower, in particular a control tower, or any other building.

[0024] The person to be protected from glare can, for example, work at a
desk or stand in the room talking to another person or move around in the
room. Further, there may also be several persons in the room. It is also
possible to protect the several persons from glare effect by the light
sources.

[0025] The at least one light source can be an external light source, for
example the sun or reflections of the sun, e.g. on a lake or a glass
front of another building.

[0026] According to the present aspect of this document, the device
comprises a dimmable panel, an optical sensor and a computation unit.

[0027] The dimmable panel has a plurality of individually dimmable cells.
The individual cells of the dimmable panel can be arranged in a matrix
form, so that a matrix of N rows and M columns is created.

[0028] The dimmable panel may, for example, comprise a LCD layer (or a LCD
film), which darkens when an electrical voltage is applied. In
particular, each of the plurality of cells may comprise a LCD layer so
that each cell can be darkened separately by applying a voltage.
Typically, a transparency of the dimmable panel (i.e., the individual
cells) is variable. For example, by varying the applied voltage, the
degree of transparency or the degree of darkening of the individual cells
can be varied. The panel is generally positioned between a position for
the persons in a room and the light source. In other words, the panel is
typically arranged within the light beam of the light source in front of
a position for the persons in a room so as to be able to darken the light
beam and thus to reduce a glare effect for the persons in a room by the
light source. Typically, the dimmable panel is attached to a glass pane
(e.g. a window pane of a building). The LCD layer may be attached (e.g.
glued) to the glass pane. However, the LCD layer may also be inserted
between a plurality of glass layers of a glass pane (for example, in the
case of a double window glass). The LCD layer may be glued as a LCD film
with the window panes, e.g. between two glass layers. A plurality of
windows with respective dimmable panels with a respective plurality of
individually dimmable cells may be coupled to form a darkening structure.

[0029] The device comprises an optical sensor (e.g. a camera) adapted to
detect an image of the persons in a room. In other words, the optical
sensor(s) are positioned in a room for detection of the persons in such a
way that, if possible, all persons in a room can be detected. The optical
sensor may comprise one or more cameras. In particular, in large rooms, a
plurality of cameras facilitates the detection of all persons in the
room. In one embodiment, the optical sensor is directed at a horizontal
angle of 20.degree. to 60.degree. into the area which is relevant for
determining the position data. For example, the optical sensor could be
attached to a corner to the ceiling. Additionally or alternatively, an
optical sensor may also be attached to a lateral position of the room (on
a wall).

[0030] The device further comprises a computation unit configured to
control the plurality of cells of the dimmable panel based on the image
sensed by the optical sensor such that a shadow is cast on the persons in
the room. In particular, the computation unit can be configured to
determine one or more shadow cells from the plurality of cells, which
cause a shadow to be cast on the persons in the room when the one or more
shadow cells are darkened when illuminated by the light source. At the
same time, the one or more shadow cells are determined to include only
the cells required to generate the shadow on the person and the devices
associated with the person (e.g. the workstation). All other cells in the
panel should remain transparent to maintain contact with the outside
area. To determine the appropriate shadow cells, the computation unit can
be configured to perform the methods described in this document for
reducing the glare effect by a light source. In particular, the
computation unit can be configured to perform the search phases and
darkening phases described below using the optical sensor and the
dimmable panel.

[0031] According to a further aspect of this document, a device for
reducing a glare effect of at least one light source to one or more
persons in a room of a building is described, the device comprising a
dimmable panel, a first optical sensor, a second optical sensor, and a
computation unit. The computation unit is coupled to the dimmable panel,
the first optical sensor and the second optical sensor. The dimmable
panel comprises a plurality of individually dimmable cells, wherein the
panel is attached to a window glass of the building. The first optical
sensor is adapted to detect a first image of the one or more persons in
the room. The second optical sensor is configured to detect a second
image of at least one light source.

[0032] The computation unit is further configured to cause the first
optical sensor to capture the first image of the one or more persons in
the room, to identify the respective position of the one or more persons
based on the first image, to cause the second optical sensor to capture
the second image of the at least one light source, to identify the
position of the at least one light source based on the second image, and
to darken one or several cells of the plurality of individual dimmable
cells based on the position of the one or more persons in the room and
the position of the at least one light source.

[0033] The dimmable panel may be the same as the above-described dimmable
panel. The above-described optical sensor can be provided as the first
optical sensor.

[0034] The second optical sensor can be almost the same as the
above-described optical sensor. Thus, the second optical sensor may also
comprise one or more cameras. However, this optical sensor is configured
to detect an image of the at least one light source. It is therefore
preferably directed outwards. It can be positioned within the room or
outside the room. Furthermore, the sensor is preferably adapted to the
expected brightness of the light source.

[0035] According to a further aspect of this document, a method for
reducing the glare effect of a light source to the persons in a room is
described. The method comprises darkening an area (e.g. of one or more
cells) of the dimmable panel. As set forth above, the panel is typically
positioned between the persons in a room and the light source (e.g. at a
window pane of a building). Furthermore, the method comprises detecting
an image of the persons in a room (e.g. by means of one or more optical
sensors directed at the persons in a room). In particular, an image of
the heads of the persons can be detected. Finally, it is determined based
on the image whether a shadow is cast on the persons due to the darkened
panel. These steps of the method can be iterated for different areas of
the panel so as to determine one or more subareas of the panel which, in
the darkened state, cast a shadow on the persons in a room.

[0036] As already stated above, the dimmable panel may comprise a cell
matrix having a plurality of separately dimmable cells, i.e. the darkened
portion of the panel may correspond to one or more of the cells. The
darkening of a portion of the dimmable panel may then comprise darkening
one or more cells of the plurality of cells.

[0037] Typically, the method comprises a search phase. In the search
phase, one or more shadow cells of the plurality of cells are determined.
The one or more shadow cells have the characteristic that by their
darkening a shadow is cast from the light source (i.e., when illuminated
from the light source) to the persons in the room. Determining the one or
more shadow cells comprises generally iterating the steps of darkening (a
portion of the panels), detecting (an image with the partially darkened
panel) and determining (the presence of a shadow on the persons in the
room) for different areas or cells of the panel. In other words, by
iterating the above steps for each of the plurality of cells of the
panel, it is determined by which of the cells a shadow is cast on the
persons in room so as to reduce the glare effect by the light source.

[0038] The search for the one or more shadow cells can use specific search
algorithms that reduce the search time. For a panel of M.times.N cells,
these search algorithms require generally less than M.times.N iterations.
For example, in one iteration, a subarea of several cells in the panel
can be darkened (for example, a row or a column or a half of the panel).
In the following iteration, the subarea can be excluded from the
determination of one or more shadow cells, if it is determined that by
the darkened subarea no shadow (when illuminated by the light source) is
cast on the persons in a room. On the other hand, in the following
iteration, the determination of one or more shadow cells can be
restricted to the subarea when it is determined that a shadow is cast on
the persons in a room.

[0039] In addition to the search phase, the method typically includes a
darkening phase during which the one or more shadow cells are
continuously darkened so as to reduce the glare effect of the light
source to the persons in a room.

[0040] To continuously adapt the determined shadow cells to a movement of
the light source, the search phase (and thus the determination of the
shadow cells) and the darkening phase (and thus the continuous darkening
of the shadow cells) can be cyclically repeated. A suitable cycle
frequency is, for example, 5 Hz, 6 Hz, 7 Hz, 8 Hz, 9 Hz, 10 Hz or more.
In order to achieve an effective reduction of the glare effect, the
darkening phase typically includes 80%, 85%, 90% or more of the total
time of one cycle.

[0041] The time of the search phase can generally be reduced if the one or
more shadow cells from one or more preceding cycles are used in
determining the one or more shadow cells in a particular cycle. Due to
the continuous movement of the light source, one or more shadow cells can
be predicted from a sequence of cycles (for example by means of motion
estimation methods). In other words, the one or more shadow cells for the
particular cycle can be predicted from the one or more shadow cells from
the one or more preceding cycles.

[0042] As set forth above, the method can be adapted to reduce the glare
effect of a plurality of light sources. In particular, the method can
determine that the one or more shadow cells comprise a plurality of
shadow cells forming a plurality of subareas of the panel. In other
words, it can be determined that the determined shadow cells form groups
or clusters, each of these clusters (subareas) can be assigned to a
corresponding light source from a plurality of light sources. That is, by
detecting clusters, the method detects the presence of a plurality of
light sources darkened by one of the cell clusters, respectively. The
method can then handle each of said clusters (or subareas) separately. In
particular, changes for the clusters can be determined separately so that
each subarea (cluster) can be predicted from a corresponding subarea of a
preceding cycle.

[0043] The method can also comprise steps for detecting a situation with
glare effect. These steps can be performed, for example, within each
cycle between the search phase and the darkening phase. For this purpose,
the method can determine an overall image comprising one or more persons
in a room and the surroundings of the persons. The overall image is
typically determined with a fully transparent (i.e., turned-off) panel.
An area of the persons in a room can be determined from the overall
image. Based on this information, a total brightness can be determined
from the brightness of the overall image (e.g., the average brightness of
the overall image) and a facial brightness from the brightness of the
overall image in the area of the face (e.g., the average brightness in
the facial area). Finally, a glare effect on the persons in a room (or
the possibility of a glare effect on the persons in a room) can be
detected by the light source based on the facial brightness and the total
brightness. For example, a ratio between facial brightness and total
brightness can be determined. A glare situation is detected if the ratio
is above a predetermined threshold value.

[0044] For shortening the search phase, it is usually advantageous if an
image of the persons in the room during the search phase is determined
only in the area of the face. The area of the face can be determined from
the overall image using pattern recognition methods. Due to this
situation, in a subsequent search phase, the detection of the image of
the persons in the room can be limited to the area of the face. A color
histogram can be used for evaluation. A facial brightness can also be
determined from the overall image, for example, as brightness of the
overall image in the area of the face (e.g. as the average brightness in
the area of the face in the color histogram). In other words, a degree of
glare by the light source can be detected. Accordingly, a degree of
darkening of the one or more shadow cells can be determined based on the
determined facial brightness.

[0045] It should be noted that the various methods and devices may be used
alone and in combination with each other. In particular, all the features
described in this document may be combined with one another in any
manner. This applies in particular to the features set out in the claims.

[0046] FIG. 1 shows, by way of example, a device 100 for reducing the
glare effect of external light sources 110. FIG. 1 shows this device 100,
by way of example, with an office room 120. It is noted, however, that
the device can be applied in any room 100 in which one or more persons in
the room may be annoyed, e.g., through a window pane 105, by one or more
light sources 110 (such as, for example, office rooms, corridors, rooms,
etc.).

[0047] The device 100 comprises a selectively dimmable panel 102, which is
capable of darkening one or more selective areas 103 of the viewing area
of the persons in a room. In addition, the device 100 comprises an
optical sensor 101 (e.g. a camera) that detects the persons (i.e., in
particular the area of the face of the persons) in a room. For this
purpose, the optical sensor 101 is arranged in front of the person (in
the viewing direction of the persons) (i.e., between the persons in the
room and the glaring light source 110).

[0048] Further, the device 100 comprises a computation unit 104 which is
capable of performing a method for reducing the glare effect of the
external light source(s) 110. For this purpose, the computation unit 104
evaluates the optical signals (e.g. the images) of the optical sensor 101
to detect a glare situation of the persons in the room. Further, the
computation unit 104 controls the panel 102 and the optical sensor 101 to
selectively darken the panel 102 in an iterative process so that a
darkening shadow 111 is cast on the person, with the darkening shadow 111
reducing or eliminating the glare situation of the person. In the case of
several light sources 110 from different directions, several darkening
shadows 111 are cast on the faces of the persons. This plurality of
shadows 111 is created by a corresponding plurality of darkened areas 103
of the panel 102. The selective darkening of the panel 102 is such that
the viewing area outside the interfering light source(s) 110 remains
unaffected. Preferably, the computation unit also recognizes individual
work devices, such as a computer screen, and selects the cells to be
darkened in such a way that the darkened cells also cast the shadow on
the work device.

[0049] System 100 may be based on methods of the optically augmented
reality (Augmented Reality) with a new perspective: instead of
positioning computer-based projections at a certain distance, as usual in
augmented reality, the system 100 darkens certain areas of the window
pane 105 by means of special algorithms and observes, in the context of a
feedback structure, the produced shadows 111 on the faces of the persons
in a room by means of an optical sensor 101 (e.g. a camera or a plurality
of directional light sensors) to determine the position of the shadows
and the contrasts in the room, i.e. in particular on the face of the
persons in room. The feedback structure, which comprises the optical
sensor 101, the panel 102 and the processing unit 104, allows (typically
within a few milliseconds) by means of the panel 102 to generate
different darkening patterns on the window pane 105 (by sequential or
heuristic darkening of certain areas/cells 103 of the panel 102) and at
the same time to determine and analyze the brightness of the person's
facial area by means of the optical sensor 101 (in real-time). By means
of suitable search methods, the number and the positions of the areas 103
to be darkened are calculated by the computation unit 104 for optimum
protection of the person. Thus, without knowing the position, the
direction and the distance of the external light source(s) 110 in
advance, the device 100 provides for determination of the locations 103
to be darkened on the window pane 105 to achieve an optimum shadowing of
the face.

[0050] Technically, the system 100 is based on a single optical sensor
(e.g., a video camera) 101 for shadow analysis. As output, the system 100
uses a selectively dimmable film 102 for shadow generation. The system
100 is self-adjusting and thus does not (or barely) require calibration.
In particular, the system 100 does not require sensors for position
detection of the external light source(s) (110). Based on a fast image
analysis, the optimum darkening can be calculated in a very brief time.

[0051] The described system 100 therefore has a high efficiency and a
simple integration. The described system 100 makes it possible to
significantly increase the performance of persons, in particular at an
office workplace. The system 100 is capable of selectively darkening
bright light effects without compromising the view of other areas of the
surroundings. On the contrary: through the suppression of the glare
effect the important contact with the outside area is maintained.
Furthermore, the system 100 makes it possible to make better use of the
outside light inside the room, thus avoiding the switching-on of light
sources within the room.

[0052] A standard video camera may be used as optical sensor 101, for
example. Such cameras can produce, for example, 50 images per second at a
resolution of 1920.times.1080 pixels. This sequence of images can then,
for example in real-time, be transmitted to the computation unit 104 via
a Gb Ethernet interface.

[0053] The optical sensor 101 is directed to the persons in the room
(i.e., in particular, to the facial area). The precise position of the
optical sensor 101 should be chosen inter alia according to practical
aspects, so that it can be easily installed in a building and the room
optic is not impaired. Above all, however, the position of the optical
sensor 101 should be selected such that the optical sensor 101 can
completely detect the entire room and, in particular, the area of the
desk and the conference area. The movement radius and/or the different
sizes of different persons can also be considered. Finally, the selected
position should allow to reliably detect brightness contrasts on the face
of the persons in the room to be able to reliably determine glare effects
and the position of the shadow 111. It has been shown that the
above-mentioned requirements can be achieved with the positioning of the
sensor 101 oblique laterally on the upper edge of a window front, for
example at an angle of 20.degree.-60.degree. to a front line. For
example, the sensor 101 could be installed in a room, for example, near
the window front center, as shown by way of example in FIG. 1.

[0054] For the above-described feedback mechanism for determining the
darkening areas 103 of the panel 102, a standard frame rate of (50-60 Hz)
is typically required. The frame rate can be achieved, for example, by
using suitable room monitoring cameras. As already stated above, it is
typically sufficient for the reduction of the glare effect according to
the method and system described herein when a glare situation is detected
in the facial area of the persons in a room and then the generation of a
shadow 111 in the facial area and below by the selectively dimmable panel
102 is detected. The frame rate of the sensor 101 can therefore be
increased by reducing the read-out area of the sensor 101 to a subarea
(ROI--Region Of Interest) of the entire detection area of the sensor 101,
wherein the selected subarea (ROI) depends on the determined facial area
of the persons in the room. Typically, the ROI is defined by the
determined facial area, including a defined surrounding (e.g. a margin of
a given number of pixels around the facial area).

[0055] To enable an increase of the frame rate by restricting the image
detection to a subarea (ROI), in one embodiment the image processing is
divided into two steps in time. In a first step, a full image detection
is performed to diagnose a glare situation and to recognize the face or
the head position. In this step, the ROI is determined. This first step
could, for example, be carried out with a frequency of 10 Hz (see
reference number 313 in FIG. 4). In a second step, the iterative
determination of the locations 103 to be darkened of the panel 102 is
then carried out (see reference number 301 in FIG. 4). Said iterative
determination of the locations 103 to be darkened should be carried out
in such a brief time that the persons in a room are not irritated, and
(2) the desired shadow 111 is cast on the person so quickly that no
noticeable disturbance occurs due to the initial glare situation. To
accelerate the iterative determination process, a frame rate as high as
possible is desirable, which can be increased by limiting the image
detection to the ROI in the second step. By limiting the image detection
to the ROI, frame rates of over 100 Hz and higher are possible so that
the iterative determination process can meet the above requirements.

[0056] It should also be noted that the possible frame rate of the optical
sensor 101 is typically also dependent on the lighting condition. Poor
lighting conditions (e.g. in the morning and in the evening) usually
require higher exposure times and consequently a lower frame rate.
Dynamic adjustment of the frame rate is typically not possible. For this
reason, the computation unit 104 can be configured such that the clocking
of the reading of the optical sensor 101 is adapted to the respective
required exposure times of the optical sensor 101.

[0057] FIG. 2 shows, by way of example, a further exemplary system for
avoiding a glare effect. In FIG. 2, two persons are in a room. As can be
seen from FIG. 2, for each of the two persons, an area of the dimmable
panel is darkened so that these areas cast a shadow on the respective
persons.

[0058] FIG. 3 shows the exemplary structure of a selectively dimmable
panel 102. The panel 102 shown in FIG. 3 comprises dimmable individual
cells 201 in a matrix form. Each dimmable individual cell 201 could
comprise a LCD layer which darkens the cell 201 when an electrical
voltage is applied. The individual cells 201 are typically configured
such that they have a transparency of 70%, 80%, 90% or more in the
inactive (transparent) state. In the active (darkening) state, the
transparency could be reduced up to 1% (or even 0.1%). The degree of
transparency can typically be controlled by the magnitude of the applied
voltage. Thus, different degrees of darkening of the cells 201 can be
achieved, as illustrated by the cells 202, 203, 204 in FIG. 3.

[0059] The panel 102 shown in FIG. 3 is composed of a plurality of
individual cells 201 in the form of a matrix, wherein each individual
cell 201 can be separately darkened. By way of example, a cell 201 of the
panel 102 could be constructed in the size 100.times.100 mm to cover the
relevant viewing area on the window pane 105 of an office room 120. For
this purpose, 120 cells 201 could be used in a configuration of 6 columns
and 20 rows. Of course, other cell sizes and panel sizes may also be
used.

[0060] The individual cells 201 can be differently darkened by the
application of a current signal. Transparent lines can be used to guide
the current signal to the individual cells 201. The electrical terminal
of the panel 102 can be laterally attached to the panel 102. The dimmable
cells 201 of the panel 102 are configured such that they enable a
virtually immediate change from the transparent to the darkened state
(and vice versa). Existing LCD layers can be darkened in the range of 0.1
ms, so that state changes with a frequency of 10.000 Hz are possible.

[0061] During the iterative process for determining the cells 201 to be
darkened, certain cells 201 of the panel 102 are darkened and at the same
time the optical sensor 101 determines whether a shadow 111 is generated
in the facial area or head area (ROI) of the persons in a room. To enable
this, the computation unit 104 is capable of synchronizing the darkening
of one or more cells 201 (by applying a voltage to the respective cells
201) and the determining an image (by reading out the optical sensor
101). As shown above, with today's cameras 101, frame rates of 100 Hz and
higher are possible and panels 102 can be operated with a darkening rate
of approximately 10.000 Hz. Thus, it is already possible to evaluate
possible darkening patterns at a frequency of 100 Hz (or more) on the
shadow 111 cast by this pattern, so as to determine, in an iterative
process, a darkening pattern of the panel 102 (i.e., a panel
configuration) which reduces the glare effect of light source(s) 110. The
following is an example of a frequency of 100 Hz.

[0062] The panel 102 typically comprises a control unit, based on which
(e.g. based on encoded telegrams) the states of all cells 201 (e.g. LCD
films) on the panel 102 can be controlled. The control unit can be
implemented as an electronic circuit board which issues, with a
corresponding telegram coding, a serial signal for a series of 120
independent AC signals (for the 120 cells 201 of the panel 102), which
are used for driving the individual cells 201. During the search for a
pattern (a pattern includes the values for all 120 cells 201 of the panel
102) which casts a suitable shadow 111 (or more suitable shadows), a list
of patterns (along with the clock frequency) may be sent from the
computation unit 104 to the control unit, which then controls a different
darkening configuration of the panel 102 according to the predetermined
patterns (e.g. with a frequency of 100 Hz). In addition, the control unit
of the panel 102 can output a sync signal which serves to synchronize the
recording by the video camera 101.

[0063] It should be noted that for the synchronization between the
individual components of the system 100 (in particular the sensor 101 and
the panel 102), respective delays should be taken into account.
Typically, there are a number of processes and transmissions of signals
that introduce a delay through digital processing. These are, inter alia,
the transmission of the serial signal of the computation unit 104, the
processing of the signal by means of the control unit of the panel 102,
the reaction time for darkening of the LCD cells 201 (0.1-0.2 ms). These
delays should be considered in generating the sync signal for the optical
sensor 101 to ensure that the shadow image detected by the sensor 101 was
generated by a particular panel pattern (rather than by a mixture of two
consecutive patterns), i.e. that the image capturing by the sensor 101
and the shadowing by the panel 102 are synchronized.

[0064] FIG. 4 shows an exemplary iterative method 300 for reducing the
glare effect of external light sources 110 by means of the device 100.
The method 300 comprises two phases. In a first (short) phase 301, a
panel pattern (also called panel configuration) is determined, which
optimally reduces the glare situation of the persons in the room. In a
second (long) phase 311, the panel configuration determined in the first
phase 301 is applied to allow a continuous reduction of the glare
situation of the persons in a room. Since both the position of the
glaring light source 110, as well as the position of the persons in a
room 120, as well as the position of the head can change continuously
with the sun's course and the passing clouds, the two phases 301, 311 of
the iterative method 300 are cyclically repeated (e.g. every 100 ms), to
adjust the optimal panel configuration continuously to the new glare
situation. This is shown in FIG. 4 by the feedback loop between the
second phase 311 and the first phase 301.

[0065] In other words, to allow for efficient darkening, in method 300 two
phases are defined in the functionality of the system 100, which are
cycled at a frequency of 10 Hz. In the first phase 301 of the cycle of
100 ms, a suitable target location of the darkening is searched for with
different patterns. In the second phase 311, the identified location of
the panel 102 is darkened to the desired degree of transparency until the
end of the current cycle (that is to the end of the 100 ms) to protect
the viewpoint of the person. Between these phases, a full image can be
taken (reference number 305), while the panel 102 is deactivated briefly
(e.g. for an exposure time of 1 ms during daytime). As mentioned above,
the full image can be used to determine the presence of a glare situation
(for detecting the glare effect) (reference number 312) and/or to
determine the position of the persons in a room (and to extract the head
position (ROI) in the image) (reference number 313). The processing
required can occur during the second phase 311, so that no delays occur
in the determination of a suitable panel configuration (for which the ROI
is typically used).

[0066] In the first phase 301 the areas of the panel are identified by
means of different strategies and based on the image analysis, which lead
to a notable darkening of the head/face area of persons in a room. The
search for a suitable panel configuration typically considers the panel
configuration used by the one or more preceding cycles to quickly
determine the currently appropriate panel configuration, assuming a
continuous situation. For this purpose, for example, motion estimation
methods known from image processing can be used to continuously adjust
the panel configuration with varying brightness changes of the light
sources 110, e.g. due to clouds and/or the movement of persons through a
room. However, if a glare effect occurs for the first time without
knowing which direction the light source 110 is coming from, the search
for a suitable panel configuration is typically more complex since no
suitable panel configurations from the past can be used.

[0067] A glare situation, where a single source (e.g. the sun) typically
causes the glare, is to be distinguished from the glare situation during
reflections of the sun through other buildings in which multiple light
sources can often cause glare at the same time. Consequently, it may be
advantageous to use a customized search strategy to determine the
suitable panel configuration depending on the situation.

[0068] In a sequential method, all 120 cells 201 can be darkened
sequentially, and it can be examined if there are any effects in the area
of the face. In a purely sequential search at 50 Hz, a cell 201 is
darkened up to 20 milliseconds per cycle. In this case, the search phase
would take 2400 ms, which means that an effective darkening (in the
second phase 311) only takes place for approximately 50% of the entire
cycle time since the rest of the cycle time is used for the search for a
suitable panel configuration (in the first phase 301).

[0069] If the sun (or a single light source 110) has a glare effect on the
persons in the room (situation without reflection) and only one area
(comprising one or more of the 120 cells 201 per window) of the panel 102
should be darkened, the following row-column search method could be used.
In the row-column search, first the complete (20) rows and then the
complete (six) columns of the panel 102 are darkened and the shadowing in
the ROI is determined for each row/column. If a shadow is determined in
the ROI for a particular row and for a particular column, the cell 201 to
be darkened is obtained by the combination of the row number and the
column number. With this method, 26 search steps (i.e., a time of 520 ms
at 50 Hz) per window pane are required. Generally, by this method, the
search time can be reduced by a factor (N+M)/N*M*number of window panes
(for a panel 102 having N rows and M columns).

[0070] As a further search method, the "divide et impera" method can be
used. In this method, the search area is divided into two halves. The two
halves of the search area are darkened one by one, and it is examined in
which of the two halves the desired shadow 111 is cast on the ROI. This
half then represents the new search area, and the method continues with a
new iteration (based on the new search area). Thus, the search area is
respectively reduced by one half in several iterations, so that in a
N.times.M panel 102 a cell 201 to be darkened can be identified in each
window pane in {square root over (NM)} steps. In each iteration, half of
the search area is set as the new search area that casts a shadow 111 on
the ROI. The identification of the target position of the darkening thus
requires approximately 8-11 iterations steps (in a panel of 120 cells),
i.e., 16-20 images of the ROI are required, which at 50 Hz can be carried
out in a time of max. 1000 ms per window pane.

[0071] Generally, the search time can be further reduced if one or more
panel configurations from preceding cycles can be used, i.e. when
previously identified panel configurations are considered during the
search. This will be explained in more detail below.

[0072] In the above examples, a cycle time of 100 ms and a frame rate of
50 to 100 Hz was used. To reduce the portion of the first phase 301 (i.e.
the search phase) of the total cycle, it could be advantageous to
increase the cycle time, i.e. to reduce the main cycle frequency (e.g.
from 10 Hz to 8 Hz, so that a cycle time of 125 ms results). This can
reduce the portion of the search phase of the total cycle to 8% for a
search time of 10 ms.

[0073] The above search methods can be adapted for the search for several
light sources. In particular, this can be necessary for reflections of
the sun through other buildings.

[0074] As mentioned above, the panel configurations from preceding cycles
can be used for the search for a current panel configuration. For
example, the search of the current panel configurations (i.e., the
current darkening areas) can be performed in the immediate vicinity of
the darkening areas already detected in the preceding cycle. The
cyclically determined reference images (full image, without darkening)
can also be used to determine the current darkening areas. As a result,
detected light/shadow movements can be detected and movement parameters
can be determined, which are considered in the search for darkening
areas. Each determined darkening area can be compared with the
corresponding reference image in each cycle. In addition to movement
information, it is thus also possible to determine whether a particular
light source is still present. If, for example, the comparison between
the image with darkening and the reference image shows no difference, the
specific light source can be classified as "no longer present". In an
exemplary method, the search can be reduced to 2% of the cycle time by
considering the reference image.

[0075] As already explained, a current panel configuration is to be
determined in each cycle as quickly as possible. For light sources 110,
which were already present in a preceding cycle, the corresponding
darkening areas from the preceding cycles can be used. In particular,
relative movement tendencies of the light sources can be determined. For
this purpose, the 3D angular speed of the individual light sources can be
determined. In addition, the directions of the light sources relative to
the head position can be determined. The two angles (horizontal and
vertical) of each light source 110 with respect to the main axis are
calculated based on the geometry of the panel 102, the camera position
101 and the position of the head (ROI).

[0076] By analyzing a sequence of darkening areas, a sequence of
associated shadow images, and/or a sequence of reference images for a
sequence of cycles, a movement of the shadow 111 can be detected on the
person's face, resulting in a movement of the corresponding light source
110. This movement of the shadow can be carried out by determining the
light variation within the images (e.g. when the brightness increases in
the area of the head). The determined movement of the shadow 111 can be
compensated for by adjustment/expansion of the darkened cells 201 of the
panel 102 so that the darkening area is tracked to the movement of the
light source 110. That is, after detection of the direction of movement
of the light sources 110, the position of the areas to be darkened can be
predicted (e.g. using a Kalman estimator). A simplified,
three-dimensional image of the room can be made by calibrating the
dimmable panel 102 and the camera 101. By determining the head positions,
the transformation between the head position and the panel is estimated.
By prediction of the darkening areas, the search for optimum darkening
areas can be skipped for the light source 110 already present, which
leads to a significant reduction of the search time in the first phase
301.

[0077] A further aspect of the system 100 is the dynamic adjustment of the
light transmittance of the darkened areas 201 of the panel 102. In other
words, the system 100 is capable of differently darkening light sources
110 with varying glare effects. For this purpose, in addition to the
association of the light source 110 with a position of the shadow 111 on
the detected reference image, an estimation of the brightness of the
respective light source 110 is also required. By correctly estimating the
brightness of a light source 110, the intensity of the darkening can be
determined dynamically.

[0078] In the realization of this function, several factors are typically
considered. On the one hand, the current exposure time of the camera 101
is considered, wherein the exposure time determines the brightness of the
head ROI. As already explained, the exposure time can be determined using
a look-up table (e.g. based on the brightness of the environment) and
applied to the camera. A second influencing variable is the degree of
darkening by the panel 102. In addition, in the case of a plurality of
light sources 110, an overlapping of the shadow projections of the
plurality of light sources 110 may need to be considered to carry out a
correct intensity allocation to the light sources 110.

[0079] In a manner similar to the movement prediction in the computation
of the position for the darkening of the individual light sources 110,
the intensities of the individual light sources 110 can also be tracked.
The intensities of the respective light sources or the intensities of the
respective darkenings are tracked based on a number of independent
parallel control circuits to realize the optimum optical filtering of the
external light sources.

[0080] The determined intensities of the darkenings are sent to the
control unit of the panel 102 (in addition to the position data) to
control the degree of darkening of the individual cells 201.

[0081] In addition to the cyclic determination of the darkening areas of
the panel 102 in the first phase 301 of the method 300, the method 300
also includes further method steps to reduce a glare effect of external
light sources 110. In particular, the system 100 should be capable of
detecting a glare effect to persons in a room. A method 312 for detecting
the glare effect can comprise, in a first step, the determination of the
average ambient lighting. Based on the available image information--by
evaluation of the full image--the total brightness of the scene as well
as the distribution of the light on the image is determined. The
brightness of the image typically depends on the exposure time of the
image. Consequently, the actual brightness of the scene/environment is
obtained as a function of the brightness determined from the image and
the exposure time of the image. This function can be determined by
empirical measurements. On the other hand, the optical sensor 101 could
comprise an auto-exposure function (i.e. an automatic computation of the
exposure time), which ensures that by adjusting the exposure time to the
actual light conditions, the actual brightness of the scene/environment
can be directly determined by evaluation of the image brightness.

[0082] In a second step, the brightness in the head area is measured. For
this purpose, the image area, which contains the head of the persons, is
extracted from the image data to determine the brightness or the
distribution of the illumination in this area. The head recognition may
be performed, for example, using an adapted version of the Bayes
classifiers (i.e. the recognition of the presence of a face, without
classification, which person is shown), as described, for example, in
"Computer Vision with the OpenCV Library", Gary Bradski, Adrian Kaehler,
O'Reilly 2008, ISBN 978-0-596-51613-0. The search for the head of a
person and a determination of a head position can be more easily
accomplished than an accurate face recognition since a recognition of an
outline of the person is sufficient. To cast a shadow on a person, a head
recognition or a recognition of an upper body is sufficient. Furthermore,
advantageously the entire head or even the entire upper body of the
person is darkened. Advantageously, the upper body is identified up to
the screen work area and darkened.

[0083] As shown in FIG. 4, the detection 312 of a glare effect is cyclic
(e.g. in the second phase 311 based on the full image determined in
method step 305). Assuming that a person does not move too far in the
work area, the head position detected in the preceding cycle can be
assumed as a start value in a search in the current full image. Also,
motion estimation methods can be used to determine the current position
of the head from a series of previous full images, which then can be
taken as a start value for recognizing the face.

[0084] In the computation of an absolute light brightness in the head
area, the actual exposure time of the camera and the brightness of the
background elements of the room are usually used in addition to the
brightness of the image area.

[0085] By examining the relation between the actual brightness of the
scene/environment and the brightness of the head area, the glare effect
on the persons can be determined. The detection of a glare situation
depending on the determined values (brightness of the scene/environment,
brightness of the head area) can be ensured by an empirically determined
classifier (by means of test persons). The output of said classifier
determines whether or not the method 300 to darken the individual cells
201 is activated. Because of the different glare situations in the
morning, noon and at night, it is advantageous to determine specific
classifiers for daytime operation and for operation at other times. In
addition, different classifiers with different degrees of sensitivity can
be determined (e.g. activation at low/medium/higher glare effect).

[0087] FIG. 5 shows another exemplary method 300 for reducing the glare
effect of external light sources 110 using the device 100. The method is
similar to the method 300, so in the following only the differences are
described.

[0088] In method 400, a further optical sensor is used (see camera 2 in
FIG. 5). The "camera 1" in FIG. 5 corresponds to the "camera" in FIG. 4.
This further optical sensor captures an image of the at least one light
source. The light source can be, for example, the sun or reflections of
the sun. This light source can be tracked. Since the light source can be
very bright, a camera suitable for this brightness is preferably used or
the camera is adjusted for this brightness so that a captured image is
not overexposed.

[0089] In method 400, the positions of the persons are identified by the
computation unit. For this purpose, a camera-related coordinate system
can be used, that is, it may be sufficient to recognize the persons in a
room in an image of a first optical sensor. Spherical coordinates can be
used, that is, only the angles under which a person appears are
considered. Said angles can correspond to a number of pixels of the
image. Based on reference sizes of humans, a distance of a person can be
estimated based on the size of the outline of a person on the image.
Alternatively, or additionally, the position of the persons in the room
can also be detected absolutely (for example, in Cartesian coordinates,
for example with respect to a corner of the room).

[0090] Furthermore, in method 400 an image of the light source is captured
with a second sensor. The computation unit, which is coupled to the
second sensor, identifies the position of the light source based on the
image of the second sensor. Here also spherical coordinates can be used,
that is, only the angles are considered at which the at least one light
source appears. Said angles can correspond to a number of pixels of the
image. The distance of the light source can be estimated or assumed as
"infinite".

[0091] The computation unit derives from the position of the at least one
light source and the position of the one or more persons, which of the
cells from the plurality of individually dimmable cells need to be
darkened, so that a shadow is cast on the one or more persons.
Preferably, the computation unit can identify the upper body and/or the
heads of the persons and select the cells to be darkened so that the
darkened cells cast the shadow on the person's head and/or on the upper
body of the person. Further preferably, the computation unit also
recognizes individual work devices, such as a computer screen, and
selects the cells to be darkened such that the darkened cells also cast
the shadow on the work device.

[0092] Finally, the computation unit controls the dimmable panel such that
a shadow is cast on the one or more persons. All other cells in the panel
should remain transparent to maintain contact with the outside area, and
the computation unit controls the panel accordingly.

[0093] The method 400 can also be repeated, since the position of the
persons and the position of the light source can change.

[0094] With the help of a detection of the positions of the persons in the
room and the position of the at least one light source, the method 400 is
accelerated with respect to method 300.

[0095] The methods shown in FIG. 5 are executed on the computation unit
104. The computation unit 104 may, for example, be implemented as an
embedded PC, digital signal processor or FPGA module (field-programmable
gate array).

[0096] Aspects of the disclosure include the following:

[0097] A device for reducing the glare effect of a light source on persons
in office rooms, the device comprising: a dimmable panel comprising a
plurality of individually dimmable cells and which is inserted into the
building window glass to cast a shadow on persons, an optical sensor
which is arranged to detect an image of the persons in a room and their
position; a sensor which detects the position of the sun or other glaring
source, and a computation unit which is configured to darken one or more
cells from the plurality of dimmable cells of the dimmable panel; to
optically detect one or more persons using the optical sensor; and to
determine based on the image whether a shadow is cast on the person due
to the darkened panel.

[0098] The above device, wherein the computation unit may be configured to
detect one or more shadow cells from the plurality of cells, which cause
that a shadow is cast on the person(s) when the one or more shadow cells
are darkened when illuminated by the light source.

[0099] A method of reducing the glare effect of a light source in the area
of the entire office room, including a desk, to persons, the method
comprising: darkening an area of the dimmable panel positioned between
the persons in an office room; capturing an image of the persons in a
room; and determining, based on the image, whether a shadow is cast on
the persons in the room due to the darkened panel.

[0100] The above method, wherein the dimmable panel may comprise a cell
matrix having a plurality of separately dimmable cells; and the darkening
of the dimmable panel may include darkening of one or more cells of the
plurality of cells.

[0101] One of the above methods, optionally further comprising: in a
search phase, determining one or more shadow cells of the plurality of
cells, by which a shadow is cast from the light source to the persons in
a room by their darkening, wherein the determining comprises iterating
the steps of darkening, detecting, and determining for different cells of
the panel.

[0102] One of the above methods, wherein optionally in an iteration a
subarea of a plurality of cells of the panel is darkened; the subarea is
excluded from determining one or more shadow cells when it is determined
that no shadow is cast on the person(s) in the room; and determining one
or more shadow cells is restricted to the subarea when it is determined
that a shadow is cast on the person(s) in the room.

[0103] One of the above methods, optionally comprising, in a darkening
phase, darkening the one or more shadow cells to reduce the glare effect
of the light source to the persons in the room; and cyclically repeating
the search phase and the darkening phase.

[0104] One of the above methods, wherein the one or more shadow cells for
the specific cycle may be predicted from the one or more shadow cells
from the one or more preceding cycles.

[0105] One of the above methods, the method optionally comprising:
determining an overall image comprising all persons in a room including
their environment; wherein the overall image is determined with the panel
switched off; and determining an area of the persons in a room;
determining a total brightness from the brightness of the overall image;
determining a facial brightness from the brightness of the overall image
in the area of the persons; and detecting a glare effect on the persons
in the room by the light source based on the facial brightness and the
overall brightness.

[0106] One of the above methods, optionally comprising: determining an
area of the persons in a room; wherein the detection of the image of the
persons is restricted to the person and the facial area.

[0107] This document describes systems and methods for reducing the glare
effect of light sources in buildings. The described systems include a
selectively dimmable panel and an optical sensor directed to the persons
in a room. They can be installed in a building with minimal effort and
are practically self-adjusting. By means of iterative feedback methods
with synchronized use of the panel and the optical sensor, shadows can be
cast on the persons, which darken a plurality of glaring light sources.
In this case, only areas on the panel are selectively darkened to not
impair the entire viewing area. The iterative methods ensure a continuous
tracking of the darkening areas to the movements of the light sources and
the movement of the persons in a room.

[0108] It should be noted that the description and the figures merely
illustrate the principles of the proposed methods and devices. Based on
the present disclosure, it is possible for the skilled person to create
various variants of the described methods and devices. These variants,
although not explicitly described, are also disclosed by this document
and are encompassed by the claims.